Arrangement with a number of units that can communicate with each other via a wireless connection system and a method for use with such a system

ABSTRACT

An arrangement comprises a number of units that can communicate with each other via at least one wireless connection system for the transmission of messages. The connection system works with first and second reception areas. A time slot system is established in a first reception area, in which system the units have access to the transmission media in question in allocated and sequential time intervals, during which the units are activated for their respective transmissions and receptions using time information executed in the time slot system, which time information refers to one or more reference times utilized in the time slot system. The means for effecting the time slot system and the respective unit concerned which is located outside the reception area can receive the said time information signals determining the reference time or reference times, which time information signals are obtained from a master time generation system with the second reception area which is larger or smaller than the first reception area. In this way, the said unit can receive the said time information signal and prepare itself completely or partially for tuning to the said time slot system before it enters into or is covered by the first reception area.

[0001] An arrangement with a number of units that can communicate witheach other via a wireless connection system and a method for use withsuch a system.

[0002] The present invention relates among other things to anarrangement for the transmission of messages comprising or operatingwith a number of units that can communicate with each other via at leastone wireless connection system. The connection system can also comprisewired communication which thereby can comprise or be supplemented byoptical communication using opto links. The messages can be of variouskinds and can, for example, concern control information (commands)and/or data, for example process data. The connection system in questioncan operate with a varying first reception area and a time slot systemestablished in this by some means (which can be already known), in whichtime slot system the units have access to the transmission mediaconcerned in allocated and sequential time intervals or time slots.During their intervals, the mobile units are activated for theirrespective transmissions and receptions by means of time informationexecuted in the time slot system referring to one or more referencetimes utilized in the time slot system. It is also referred to thepreamble of claim 1. The invention also relates to a method associatedwith this.

[0003] The invention can be used in connection with so-called fieldbusses, that is with systems of, for example, the type CAN (ControllerArea Network) and CAN Kingdom (developed by the Applicant of the presentpatent application). The invention also relates to systems that operatewith signal protocol in connection with this and radio links, where forexample Bluetooth can be mentioned. Reference is made to the literatureand patents in connection with the said systems. Reference is made, forexample, to the Swedish patent application 000111486 submitted by thesame Applicant and to EP 513137 and EP 470199. Reference is also made tothe Swedish patent application “An arrangement in a distributed controlsystem for increasing the availability of data and/or control commands”submitted by the same Applicant on the same day. Reference is also madeto IEEE 802.11 for the utilization of jumping frequencies or correlationcodes (Direct Sequence Spread Spectrum).

[0004] In accordance with the invention, a mobile unit must be able toenter a first reception area and connect to existing signal protocol inthis, in order to be able to communicate with units that are inside thearea. In addition or alternatively, a fixed or mobile unit must be ableto be covered by a first reception area which moves in relation to theunit and in a corresponding way must also be able to connect to existingsignal protocol in order to make possible communication with other unitswithin the area. A problem associated with this is that with existingsystems or signal protocols, for example the Bluetooth protocol, thereare long hand-shaking times between entering units and/or covered unitsand the functions/units already in the system. It can be mentioned inthis connection that hand-shaking times can be up to 10 seconds incurrently existing systems. The invention intends to solve this problemand proposes arrangements and methods which will reduce to aconsiderable extent or completely the hand-shaking times in question,which thus means that existing units outside the area can communicatewith other units essentially immediately when they enter or end upwithin the reception area in question.

[0005] There are requirements concerning the ability to constructservice systems, for example road tolls, service stations, for examplein association with petrol stations, garaging arrangements, etc, whichmake possible rapid or immediate contact between a unit outside thesystem and the units which are inside the system. The invention is alsointended to solve this problem.

[0006] In this connection, it can be necessary to obtain verificationsor approval of the unit or units in question which are entering orcoming inside the system and requesting to communicate with existingunits already inside the system. There is also a need to be able toincrease the security aspects in connection with the said entering of aunit into or coverage of a unit by the reception area concerned. Theinvention is also intended to solve this problem.

[0007] It is essential that proposed measures can be incorporated in thefunctions of the systems utilized so that these do not need to besubjected to considerable modification and to be allocated newfunctions. The invention is intended to solve this problem and proposesa technically simple and also economically advantageous solution inassociation with systems of the said type.

[0008] The principle characteristics of the arrangement according to theinvention include i.a. that the arrangement comprises a network area, inwhich the units exercise their communication in a network, and that therespective unit is adapted to identify and receive information relatedto a radio protocol including ruels for time slots and selection offrequencies in the time slot system and information of a used type of atime reference system, for example GPS, valid for the arrangement. Thearrangement also includes an reference time area, which works with thesaid time reference system and at least one unit is adapted to identifysaid reference time area and synchronize itself to the reference time bymeans of said type information. Said at least one unit is adapted to setits own internal clock in dependence of the reference time and to causea time generating function in the communications between the unitswithin the network area, and the reference time will in such a way beadapted in a separate or independent way from said communications of theunits in the network. In an alternative arrangement first units areadapted to establish or be included in two or more geographicallyseparated local networks and the respective local network includes areference time area. The respective reference time area is then adaptedwith a time reference system, for example GPS, selected among a numberof possible time reference systems. Respective unit of second unitscomprises or constitutes a mobile unit in a stationary local network ora mobile or stationary unit in a mobile network. Respective unit of thesecond units is adapted to identify respective reference time area a andto receive information about its valid type of the time referencesystem. At least one of said second units is adapted to have itsinternal clock set or actuated by said reference time, which in such away is adapted to be separated from or independent of the communicationsof the units in respective network.

[0009] At its connection procedure to the arrangement respective unit isbodily inside or outside said network area and/or said time referencearea. Then the unit is adapted to work with a first stage for connectionto the actual radio protocol, a second stage for entrance into oridentification of the referens time area, and a third stage in which thetime generating function is performed between the internal clocks of theunits. By means of the time generating function, the units are adaptedto assume actuated positions or conditions for transmission andreception of their messages and to assume not actuated positions orconditions in the case without any transmission or reception. A schemaor time schedule for the appearance of the time slots in the time slotsystem is adapted to attain allotment of the time slots to the units inconnection with the actuated positions or conditions of the units inorder to make it possible to allot the units to their time slots withoutany essential time related data in the transmitted or received messages.The unit or the units, the clock or clocks of which is or are,respectively, set or influenced by the reference time, can in its ortheir turn operate or operates as time master or time masters to thatunit or those units of the actual units which do not have been set orinfluenced by the reference time.

[0010] In an embodiment an arrangement according to the invention can beconsidered to be, among other things, that both the means forimplementing the time slot system and the unit concerned which islocated outside the reception area can receive time information signalsdetermining the reference time or times in question obtained from amaster time generation system, which can consist of, for example, theGPS system (Global Positioning System) which has a second reception areathat can be larger or smaller in area than the first reception area. Thesaid unit is thereby arranged, upon receipt of the said time informationsignal, to prepare itself completely or partially for tuning to the saidtime slot system before it enters into or is covered by the firstreception area.

[0011] Thus the said reference time or times can be considered toemanate secondarily from master time generation which is arranged withina second reception area which thereby can be situated inside the firstreception area. A unit which is located or which ends up outside thefirst reception area (due to variation and/or movement of the firstreception area and/or movement of the unit) obtains the reference timeindication in the first reception area when the first reception areacovers the unit or when it enters into the first reception area.Updating and maintaining of accuracy of the first reception area'sreference time or times can be carried out by one or more unitsentering, being covered by or being located in the second reception areaat least temporarily for a predetermined minimum time interval andobtaining transformable updated reference time or times for other mobileunits in the first reception area.

[0012] The invention can thus be considered to comprise or consist of asystem that establishes a common global time-keeping for a system. Eachnode can thereby have its local time which is either synchronized to orrelated to the global time. A schedule with time slots referring to theglobal time for transmission and reception of messages is drawn up forall the nodes in the system. The time slots that are allocated to themessages that the node is to transmit or receive can thereby bedistributed to each node in such a way that sender and destination ordestinations of the majority of messages can be determined just fromknowledge of the system's schedule, the common global time-keeping andthe time slot in which the message is sent.

[0013] In a further embodiment of the arrangement according to theinvention can be considered to be, among other things, that the firstunits are arranged to form two or more geographically separated localnetworks which operate with essentially the same signal protocol andthat the local networks also operate with the same time synchronizationand reference times which can be determined from a master timegeneration system, which can consist of the GPS system or otherestablished system. The respective second unit, that consists of amobile unit in the case of a fixed local network or of a mobile or fixedunit in the case of a mobile local network, is arranged to receive timecontrol from the master time generation system when it is in a positionoutside the reception area of the respective local networks and toutilize the received time control to prepare itself completely orpartially for tuning to the said time slot system before it enters intoor is covered by the said reception area.

[0014] Further developments of the invention will be apparent from thesubsidiary claims concerning the arrangement described above.

[0015] The principle characteristics of a connection method according tothe invention can be considered to be, among other things, that a givensignal protocol for the system is obtained by the mobile unit inquestion which is to enter or be covered by the reception areaconcerned. Synchronization of the unit to the system's global time iseffected. If allocated time slots are thereby obtained already upon theobtaining of the said signal protocol, transmission/reception inaccordance with the protocol can commence directly or immediately. If,however, the allocated time slots in question are not obtained, the timeslots can be obtained according to rules which are to be found in thesignal protocol above, after which transmission/reception according tothe protocol can then commence.

[0016] Further developments of the method in question are apparent fromthe following subsidiary claims concerning the method.

[0017] The system can comprise different types of connections, wirelesslinks and wired links. Wired links also include optical connections viaopto links. The transmission of messages can take place in differentsteps, for example, in two steps from wireless transmitter to wirelessreceiver and from wireless receiver to wired link. Alternatively, threesteps can be used, namely from wired link to wireless transmitter(s),from wireless transmitter to wireless receivers per channel and fromwireless receivers to wired link.

[0018] The wireless transmitters each transmit on their own “channel”(frequency channel). A channel is characterized in that, whentransmitting, each transmitter has access to a part of the availablebandwidth in the ether which is exclusive to the system. The exclusivitycan be an allocated frequency in a time interval, for example as in theknown Bluetooth protocol or IEEE 802.11 for jumping frequency or acorrelation code as in IEEE 802.11 Direct Sequence Spread Spectrum. Atransmitter and one or more receivers can operate on one and the samechannel during one and the same time interval.

[0019] Nodes can be connected both to the wireless network and to thewired network and are called g-nodes. They act as “gateways”, that isthey receive a complete message on the wireless link and ascertain in aknown way that it has been correctly received, by means of check codes,error-correction codes, etc. Thereafter the message is transmitted onthe wired link. Each message has an identity on the respective mediumwhich is at least unique for that transmission occasion. The identitycan be a bit code or can consist of a particular time slot in ascheduled system or a combination of these methods. The identity can becommon or different for the two media. If they are different, theassociation between the identities is known by the respective g-node(see below). Such an association can be made in a plurality of ways,some of which are described in the patent referred to.

[0020] The Bluetooth protocol can be modified so that several slaves areallocated the same time slot for reception. A CAN message (here an LLCdata frame) is generated in a PC equipped with a radio interface of theBluetooth type. The CAN message is packaged as data in a Bluetoothmessage which is sent by the PC and received by two or more g-nodes. Theg-nodes that have received the CAN message error-free according to theBluetooth protocol's error-detection mechanisms thereafter send out theCAN message on the CAN bus. If several g-nodes commence theirtransmission synchronized to the same Strat of Frame (SOF), they willsimultaneously send the message bit by bit, which will work because themessages are identical. If any g-node or g-nodes can not synchronize tothe message that the first g-node sends, then they change over intoreceiving nodes in accordance with the CAN protocol. They will thenreceive a message that is identical to the one they were in the processof sending. When they have ascertained that such is the case, theyrefrain from sending their message. There is thus parallel redundancyfor signalling from the PC to the CAN network. In the oppositedirection, serial redundancy can be achieved. Each g-node is allocated atime slot for transmission and information about which CAN identifieridentifies the CAN messages that are to be sent to the PC. At the sametime, they obtain the messages on the CAN bus in accordance with the CANprotocol. The messages that are to be sent to the PC are packaged asdata in a Bluetooth message that is sent in the respective time slot.The PC then receives one or more identical messages from the CAN system.This method is here designated “P-presentation”.

[0021] If information is required about which recipient has received thestrongest signal, the following procedure can be applied. It assumesthat the radio part of the g-nodes provides a value for the signalstrength, (signal strength indicator, SSI), for example a measurementvalue 0-255. The CAN identifier is then divided into at least threefields (see FIG. 5 below). One which contains the value 255-the SSIvalue, one which indicates which g-node is sending the message and onewhich indicates that it is one (of several) messages from the PC. If nowthe SSI value-255 is inserted first in the CAN identifier, the g-nodethat has the highest signal strength will gain access to the bus if allthe g-nodes commence signalling simultaneously. The information aboutwhich g-node has the strongest signal and the actual value of this isthus to be found in the CAN identifier and is thus available to allnodes that can use this information. FIG. 5 shows an example oforganisation of CAN identifiers by signal strength, the identity of upto 16 g-nodes and the identity of up to 64 messages from the PC. Moreinformation about how CAN identifiers can be constructed to give therequired characteristics is to be found in the specification forCAN-Kingdom. This method is called “SSI-presentation”.

[0022] According to the invention, a mobile transmitter can be used. Inthe first position it has contact with two receivers, then three,thereafter two. Maximal transmission reliability is ensured in a simpleway by means of P-presentation. Using SSI-presentation, it is alsopossible to obtain a good idea of where the mobile transmitter islocated. Examples of combinations of a mobile transmitter and a fixednetwork can be a car in a garage, a car at a service station, anignition key (or corresponding item that can comprise a similarfunction, for example a mobile phone, identity card, etc,) for avehicle/car/tractor/excavator/etc. Signal strength indication can beused in association with indication of bit errors. In the event of aso-called multipath situation (several signal paths), messages witherrors can be obtained, in spite of the signal strength being high. Themessages with errors can be detected by the error-detection mechanism inthe protocol as bit errors in the message. If the error persists, theconclusion can be drawn that there is a multipath situation and measurescan be implemented in the form of a change of transmitter, transmitterposition, amendment of propagation diagram, etc. This also ensures thatthe approval by the different networks of the different entering unitsor covered units is technically simple.

[0023] A currently proposed embodiment of an arrangement and a methodaccording to the invention will be described below with reference to theattached figures in which

[0024]FIG. 1 shows in diagrammatic form and in a horizontal view, firstand second reception areas where nodes are located inside the areas andwhere a node which is located outside the nodes is in the process ofentering or being covered by the system or the networks,

[0025]FIG. 2 shows in diagrammatic form and in a horizontal view, asecond embodiment of the network and reference system,

[0026]FIG. 3 shows in diagrammatic form and in a horizontal view, how avehicle on a road interacts with advertising boards or the like arrangedalong the road,

[0027]FIG. 3a shows in diagrammatic form and in a horizontal view, adifferent embodiment in relation to FIG. 3,

[0028]FIG. 4 shows in diagrammatic form and in a horizontal view, a roadtoll system,

[0029]FIG. 5 shows in diagrammatic form, an example of the constructionof a type of message, and

[0030]FIG. 6 shows in diagrammatic form and in a horizontal view, anembodiment with local networks in the form of petrol stations and mobileunits in the form of customers and staff at the petrol stations.

[0031] With the Bluetooth system (Bluetooth protocol) it can take a longtime for a unit entering into a pico-network to synchronize itself tothe network in question. This problem can be solved by a modification ofthe Bluetooth protocol combined with GPS and certain prior information.The arrangement and/or the method can be used by all vehicles withnavigation systems based on accurate time, for example GPS, whichtransmit a very accurate time indication once per second. Based on aradio system of the Bluetooth type, this operates with symmetrical timeslots where each time slot is 2.5 ms. The system jumps between fivefrequencies, A, B, C, D and E. For the sake of simplicity, it is assumedthat the frequencies are taken in turn. The stationary unit commencesthe time slot with the time to with the frequency A for transmission,t+2.5 ms A for reception, t+5 ms B for transmission, t+7.5 ms B forreception, and so on. By knowing the time t and the algorithm for timeslots for transmission and reception and for frequency jumping, anymobile node can be pre-synchronized to a fixed system. It is easilyrecognized that more complex algorithms and sequences can be used forsynchronization of mobile units entering fixed systems. Once the mobilenode has been incorporated in the fixed system, there is no longer theneed for the mobile node to be able to be directly synchronized to thereference time system. It is sufficient for it to be synchronized to thefixed network, which in turn is synchronized to the reference timesystem. The main idea is that the fixed system has a previouslydetermined behaviour in relation to the time in a reference time base.As this reference time base has a larger geographical extent than thefixed system, a mobile node can synchronize itself to the system as soonas it can synchronize itself to the time in the reference time system.This concept can be extended to completely virtual systems, where nodesprogrammed to be able to operate in a particular system do so when theycome within range of other nodes which are programmed for the samesystem. Here it can of course be assumed that the individual nodes havea larger geographical extent than the reference time system. It is thenthe geographical area of the reference time system that limits theability of the mobile nodes to synchronize themselves to the system.

[0032] A salient feature of the invention can be that a time masteraccording to a known system has been separated from other protocolproblems. Other functions can be solved in the usual way and thesolutions found can be communicated to the nodes that are to interact.The reference time base can be GPS, but there are many otheralternatives.

[0033] Using the invention, it is simple to construct service systems,for example, road tolls, service stations, garages, etc. As the localnetworks are small geographically and well separated from each other,all can work in a synchronized way. All the service stations of a petrolcompany can have the same protocol for frequency jumping, time slots,etc, and can work synchronized in time. Upon signing an agreement, thecompany's customers can receive the necessary information about theprotocol and can thus be phased in to the network immediately whenvisiting any service stations belonging to the company. The informationrequired can be distributed in many ways, for example via the Internet.

[0034] In one embodiment, a unit that is not yet connected can listen ona fixed frequency where it knows that time messages can appear. Thesecan, in addition to the time, also contain a heading which identifiesthe system. In this way, the unit that is not yet connected cansynchronize itself to the network on the messages that are sent in orderto maintain the global time in the system.

[0035]FIG. 1 shows how a movable or mobile unit 1 is about to enter afirst reception area 2 which can consist of a network area. In theposition shown in FIG. 1 outside the network area, the mobile unitobtains information about the signal protocol which exists or isutilized within the area 2. The signal protocol information can beobtained in various known ways. In a first alternative, the mobile unitcan have internal selection options for selecting different signalprotocols. Alternatively, the protocol information can be transmittedfrom a unit 3 via a connection 4. The connection can, for example,consist of a radio frequency link and in FIG. 1 a message is indicatedby 5, by means of which message the information of i.a. the type ofreference time is transferred. The mobile unit moves in a directionindicated by 7 towards the network area in question. In this case, thesystem operates with a reference time area or another reception area 8which is larger in size than the area 2. At the position of the mobileunit 1 within the reference time area, which position is indicated by 1′and broken lines, the unit can synchronize itself to the time of thereference time base. This synchronization can be carried out in a knownway in accordance with the above. The direction of the messagetransmission from the master time generation system concerned isindicated by 10. In this embodiment, the time generation system consistsof the GPS system, which has been symbolized in FIG. 1 by GPS. Thenetwork system 2 also knows about the time generation in question fromthe master time generation system. In FIG. 1, the transmission from theGPS system is symbolized by the message 11 which is transmitted in adirection 12 towards the network system. In the network system there aremeans 13 for synchronization functions. The said means 13 are onlyindicated symbolically and can be arranged in a known way overall in abase station and/or arranged in or at one or more units 14, 15 which canbe fixed and/or mobile. When it enters into the network system 2, themobile unit has thus all the necessary information it requires in orderto be able to operate within the network 2. When the mobile unit 1′ islocated within the area 2, traffic can already pass between fixed and/ormobile units 14, 15 within this area and the unit which has now enteredor which has just entered can communicate immediately with other unitswithout handshaking procedures needing to be implemented with these.Thus the unit 1, 1′, 1″ prepares itself for tuning to the time systemand time slot system before entering into the area 2, which thus makesthe hand-shaking procedure unnecessary upon the actual entry into thearea 2. In this case, the different units within the area 2 communicatevia radio links which are symbolized by 16 and 17. The units areequipped with transmitter, receiver, antenna and other equipment in aknown way. In this case, a mobile unit 1 has been described which movesrelative to the areas 2 and 8 in question. Alternatively, one or both ofthe said areas can move relative to the unit 1, which can then be fixedor mobile. In this case, the direction of movement of the respectivenetwork is indicated by 18.

[0036] In accordance with FIG. 2, the reference time area 8 a can have asmaller extent than the network area 2 a, that is the first receptionarea 2 a has a larger extent than the second reception area 8 a. As inthe previous case, the mobile node 1 a obtains the requisite protocolinformation outside the time reference and network areas. The protocolinformation can be derived in a corresponding way to the case shown inFIG. 1, for example internally in the mobile unit 1 a or from anexternal unit or an external system 3 a. In this case, the direction isindicated by 4 a. The unit 1 a enters the network area 2 a, but can notsynchronize itself to this as the unit is not synchronized to thereference time system. Once inside the reference time area, that is inthe position shown by 1 a′, the unit can synchronize itself to thereference time and when this has taken place, the unit can derive thecorrect frequencies and time slots according to the radio signalprotocol utilized and thereby connect to the network area 2 a usingother protocol information. Once synchronized to the network 2 a, it canleave the reference time area and in accordance with the system utilized(CAN, CAN KINGDOM, Bluetooth, etc) it is sufficient for the unit orunits that are inside the reference time area to be synchronized to thereference time. The units connected to the network outside the referencetime area can maintain the synchronization by using the time slots ofthe units synchronized to the reference time as a secondary referenceindicator. Any one unit, for example 14 a, in the network must, however,return inside the reference time area for re-synchronization before thetime slots in the system fall outside an acceptable tolerance level. Theunit 1 a can thus leave its position 1 a′ and assume a position 1 anoutside the reference time area 8 a and establish communication withother units 14 a, 15 a, 15 b. Also in this case, a time generationsystem in the form of GPS can be utilized. In FIG. 2, thesynchronization function is indicated or symbolized by 9 a. Thesynchronization function for the network which is indicated by 19 inFIG. 1 has been symbolized by 19 a in FIG. 2. In FIG. 2, the radio linksbetween the different units are indicated or symbolized by 17 a, 20 and21, which links are thus established using channel frequencies in aknown way.

[0037]FIG. 3 shows an example of the use of the invention along a roador a section of road 22. Means for emitting information and/or receivinginformation are arranged at a distance from each other along the road.In the present case, the means consist of a number of advertising boards23, 24, 25 which comprise fixed nodes 23 a, 24 a, 25 a with radiotransmitters and/or radio receivers in accordance with the above. Therespective transmitters/receivers have reception areas 23 b, 24 b, 25 b,which reception areas do not overlap, for which reason they can all havethe same frequency jumping and time slots and can work in a synchronizedway. Each has access to the reference time system, which can hereadvantageously consist of the GPS system. The time synchronizationsystem for the fixed units is symbolized by 26, 27 and 28 respectively.A car 29 moves along the section of road 22 in a direction 30 and inFIG. 3 the car's positions in the different areas 23 b, 24 b and 25 bare indicated by 29, 29′ and 29″ respectively. The car or vehicle issynchronized to the reference time system 31, which synchronization issymbolized by arrows 32, 33, 34. When passing the advertising boards 23,24, 25, the car 29 can receive messages from the advertising boards inits different positions. The contact can be two-way and information fromthe car can thus also be transmitted to the advertising boards. Thecoverage area for an advertising board can typically be 30 metres alongthe road, which provides approximately 1 second of effective contactwith the car if the car is travelling at 100 km/hour. The messagesbetween the car and the advertising boards are exchanged in accordancewith the utilized signal protocol. In one embodiment, the messages froman advertising board can be one-way and can be sent as one packet pertime slot, where each packet is numbered, for example from 0 to 64, andsent in a continually circular sequence. In the car they can later bedisplayed in the order 0 to 64, regardless of where in the sequence thereception commenced. In FIG. 3, the radio links (the channelfrequencies) are symbolized by 35, 36 and 37.

[0038] A more advanced example is shown in FIG. 3a, where coverage areas23 b′, 24 b′, 25 b′ of the advertising boards 23′, 24′, 25′ respectivelyare partly overlapping. Also in this case, the advertising boards or thelike comprise fixed nodes or radio transmitters/receivers 23 a′, 24 a′and 25 a′ respectively. The advertising boards 23′, 24′ and 25′ interactin accordance with FIG. 3a in a common network and the time slots mustbe divided between them, as, for example, the unit 24 a′ is covered byboth the areas 23 b′ and 25 b′. Only one unit, for example the unit 23a′, needs to have been synchronized to the reference time system whichalso in this case can consist of GPS. Other units can synchronize on thetime slots in the network and this network synchronization is symbolizedby 31′. If the network is enlarged by a fourth unit, for example afterthe unit 3, this fourth unit can reuse the frequency and time schedule,etc, of the unit 23 a′. In FIG. 3a, the radio links between the car andthe respective advertising boards at the different positions of the carare indicated by 35′, 36′ and 37′ respectively. In this case, there arealso radio links between the units 23 a′, 24 a′ and 25 a′, which radiolinks are symbolized by 38 and 39.

[0039] In accordance with FIG. 4, the invention can be used inconnection with road tolls or the like. A number of lanes, for example,parallel lanes 40, 41 and 42, are arranged or created. Each lane, forexample lane 40, is provided with traffic lights, for example two setsof traffic lights, 43, 44, one at the entrance 40 a and one at the exit40 b of the respective lane. At the entrance and exit, 40 a and 40 b,are arranged sensors, 45 and 46 respectively, which sensors are arrangedto detect the passing of a vehicle or car. In addition, the respectivelane has a local wired network 47 which is connected to a lanecontroller 48, to the traffic lights 43, 44 and to a number of radiounits 49, 50, 51, 52 which are sequentially overlapping. The lanecontrollers in the different lanes are in turn connected to a wirednetwork 47′, which is connected to the charging system 58 belonging tothe owner of the road via a road toll unit. When there is no car in thelane, the light arrangement 43 at the entrance 40 a shows green and thelight arrangement 44 at the exit shows red. When a car 55 driving in thedirection 56 passes the sensor 45, the light system 43 changes to red.The car 55 then passes the radio units 49, 50, 51, 52 which work in asynchronized way. While it passes, requisite information is exchanged,for example such information that enables the road toll in question tobe able to be charged. When the exchange of information has beeneffected, the exit light or exit light arrangement changes to green.When the car passes the exit sensor 46, the lane returns to its originalstatus. By several radio units working in a synchronized way, aredundant connection is achieved to the passing car with good range inthe longitudinal direction of the road, but with a limited range in thetransverse direction. The propagation diagram, can, in accordance withthe above, be further Improved by the use of directional antennas. Inthe figure, the radio units have been grouped in order to minimizecrosstalk and message packet collisions between the lanes. In analternative embodiment, the time slots can be coordinated, so thatcrosstalk or message packet collisions are avoided or do not occur. Inaccordance with FIG. 4, the fixed radio units 49, 50, 51, 52 aredisplaced along the longitudinal direction of the lanes, whereby in thecase shown the radio units in the central lane are located closer to theentrances 40 a of the lanes than the fixed units of the outer laneswhich are located closer to the exits 40 b of the lanes. In this way,the distance between the reception areas can be increased and the dangerof crosstalk or message packet collisions is avoided. In FIG. 4, a wiredlink is indicated by 57, which can lead from the unit 54 to a chargingsystem 58 at a distance from the lanes in question. The unit 54 canthereby act as an adaptation unit between the fixed network and thecharging system. Alternatively, the link 57 can consist of a differenttype of connection, for example a wireless link.

[0040] The advantage of, for example, using phase-displaced layouts isobvious. One category of mobile unit can thereby follow a first scheduleand another category can have a second schedule. Radio apparatusinvolved can transmit simultaneously and frequency jumping can beeffected at the same time, which frequency jumping can thereby still becarried out at random. The time base is shared and known and a referencesystem is used. The invention is thus based on distributed schedulingand can be made orthogonally independent. The system can separate timeor frequency and a utilized time slot or slots can be divided up and thetransmission can be directed. The transmission can thereby be directedtowards a car or a vehicle in such a way that it does not reach a car orvehicle that is adjacent or close by. When detection of the signalstrength is required, it is not sufficient in all cases in accordancewith the above to detect only the signal strength (cf. multipath). It isa case of ascertaining where there is a reflection and of changing thecar or vehicle's antenna propagation and/or direction. Error-detectioncodes can thereby be used, and the call direction can be changed, theunit position can be changed, etc. To carry out the functions describedabove, there is thus an original basic system on which is based thedefinition of new schedules, jump algorithms, etc. Interpretation can becarried out of information in each time slot with regard to whichfrequency is to be used in the slots, the jump schedule, algorithms,etc, outputs, choice of antenna, dispersion area, etc. By means of theproposals above, the system is not dependent upon working with a beaconsignal to which it must be related. With such a beacon signal, the riskof interference is considerable and in the case where this signal isabsent, the whole system is reset, which is not the case with thesystem/network according to the invention.

[0041]FIG. 5 shows an example of a construction of a message type inaccordance with the above, with reference to what was discussed above.In FIG. 5, the message is indicated by 59 and comprises a first part 60that consists of an SSI value, a part 61 that consists of a g-nodeidentifier, a part 62 that indicates the PC message number and a part 63with additional data.

[0042]FIG. 6 shows a concrete example of the present invention based(completely or partially) on the principles, functions and/orconstructions described above. FIG. 6 shows three local networks 64, 65and 66, for example in the form of petrol stations. The stations areseparated geographically in a known way and operate with essentially thesame signal protocol, see above. The local networks also operate withthe same time synchronizations and reference times that can bedetermined from a master time generation system which can consist of theso-called GPS system, see also the example described above. The localnetworks comprise first units, for example, the units 67 and 68. Theseunits can be fixed and can communicate with each other via connectionsthat can consist of fixed connections, radio links, etc, not shownspecially in FIG. 6, see also above. The local networks also work withmobile or fixed second units, which are represented by 69, 70, 71 inFIG. 6. These second units can be divided into different categories, theunit 69 representing a category that comprises staff and the units 70and 71 comprising or representing mobile customers of the local networkin question. The customers are to be served by the local network or thepetrol station in accordance with the above. The respective localnetwork can be entered by mobile units which are outside the referencearea of the local network, see above. In FIG. 6, a mobile unit/customer72 is about to enter the local network 64, note the direction 73. Inaccordance with the above, the mobile unit 72 obtains information aboutthe existing signal protocol in the network 64. In FIG. 6, this receiptof information is symbolized by 74, 75. The local network 64 alsooperates with a function for approval of the mobile unit 72 before thisis connected by the protocol and the reference times in the network 64.In a corresponding way, the mobile unit 76 can enter the network 65 inthe direction 77. Prior to entry into, or approval by, the network, etc,the mobile units obtain reference time information from the master timegeneration system, for example the GPS system. In FIG. 6, thistransmission of information is symbolized by 79 and 80. The respectivemobile units 72, 76 (which can consist of customers/staff) thus receivetime control from the master time generation system while in a positionoutside the reception area 64′, 65′ of the respective local network andutilize the received time control 79, 78 in order to prepare themselvescompletely or partially for their tuning to the time slot system used inthe respective local network before they enter into the said receptionarea. The respective local network can thereby operate with a time slotsystem where the schedules are phase-displaced in frequency or time ineach time slot and the channel frequencies thus obtained in therespective time slots are allocated to the different categories(customer/staff). The customers can in turn be divided into differentcategories. A first channel frequency can be allocated to the localnetwork's customers and a second channel frequency can be allocated tothe local network's staff, and in a similar way different categories ofcustomer can have different channel frequencies. In accordance with theinvention, the algorithms for channel frequency jumping can beconstructed in such a way that the different channel frequencies in therespective time slots jump at random simultaneously and equally. Thusthe arrangement also operates here with distributed scheduling andseparation of different categories (customers/staff). The separation iscarried out in time and/or frequency and the transmissions in the mobileand any fixed radio apparatus (transmitter/receiver) can operate withdirected transmissions so that, for example, customer apparatus in closeproximity to other customer apparatus will not be subject tointerference. Detection of the signal strength can be utilized in theerror-detection function and in certain cases, particularly in the eventof a multipath situation, the error-detection code in the signalprotocol, changing of the antenna propagation and/or antenna directionare also used. In FIG. 6, a time slot is shown symbolically by 74′. Thetime slot in question is divided into two parts, one representing afirst channel frequency 71′ and the second representing a second channelfrequency 72′, which first and second channel frequencies can thus beallocated to two different categories in the context concerned.

[0043] Said time generating function, which relates to the internalclocks of the unit, can operate in a way known in itself, compare theabove mentioned prior art, the system CANKINGDOM provided on the marketby KVASER AB/SE, etc. There is no need for the time reference system tobe involved or dependent with the network or protocol. The timereference system can for example supplementary be used for otheroperations in the system than setting said clock or clocks of the units.By said independence of the reference time it is not possible to use thebeacon signals, which have to be initiated in the right way all the timein order to prevent disturbances in the communications of the units.Only the type information 6 is necessary in the present case forindication of the type of reference time used in the case. The globaltime of the system can be seen as separate from the protocol (network).The actual time is put in relation to the time schedule.

[0044] The invention is not limited to the embodiment described above byway of example, but can be modified within the scope of the followingclaims and invention concept.

1. An arrangement with a number of units that can communicate with each other via a wireless connection system for transmission of messages which comprise control informations (commands) and/or data, and wherein the units have access to an actual transmission medium in sequential time intervals, at the intervals of which the units can be actuated for their respective transmissions and receptions by means of a time slot system, characterized by one or both of the following alternatives; a) in that the arrangement comprises a network area, in which the units exercise their communication in a network, in that the respective unit is adapted to identify and receive information related to a radio protocol including ruels for time slots and selection of frequencies in the time slot system and information of a used type of a time reference system, for example GPS, valid for the arrangement, in that the arrangement also includes an reference time area, which works with the said time reference system, in that at least one unit is adapted to identify said reference time area and synchronize itself to the reference time by means of said type information, in that said at least one unit is adapted to set its own internal clock in dependence of the reference time and to cause a time generating function in the communications between the units within the network area, and in that the reference time in such a way is adapted to be separated or independent from said communications of the units in the network, b) in that first units are adapted to establish or be included in two or more geographically separated local networks, in that respective local network includes a reference time area, in that respective reference time area is adapted with a time reference system, for example GPS, selected among a number of possible time reference systems, and in that respective unit of second units comprises or constitutes a mobile unit in a stationary local network or a mobile or stationary unit in a mobile network, in that the respective unit of the second units is adapted to identify respective reference time area a and receive information about its valid type of the time reference system, and in that at least one of said second units is adapted to have its internal clock set or being actuated by said reference time, which in such a way is adapted to be separated from or independent of the communications of the units in respective network.
 2. Arrangement according to claim 1, characterized in that the respective unit at its connection procedure to the arrangement is bodily inside or outside said network area and/or said time reference area and is adapted to work with a first stage for connection to the actual radio protocol, a second stage for entrance into or identification of the referens time area, and a third stage in which the time generating function is performed between the internal clocks of the units.
 3. Arrangement according to claim 1 or 2, characterized in that, by means of the time generating function, the units are adapted to assume actuated positions (conditions) for transmission and reception of their messages and to assume not actuated positions (conditions) in the case without any transmission or reception, and in that a schema (time schedule) for the appearance of the time slots in the time slot system is adapted to attain allotment of the time slots to the units in connection with the actuated positions (conditions) of the units in order to make it possible to allot the units to their time slots without any time related data in the transmitted or received messages.
 4. Arrangement according to claim 1, 2 or 3, characterized in that the unit or the units, the clock or clocks of which is or are, respectively, set or influenced by the reference time, in its or their turn operate or operates as time master or time masters to that unit or those units of the actual units which have not been set or influenced by the reference time.
 5. An arrangement according to any of the preceding claims, characterized in that the units are mobile and can end up outside the first reception area due to variations and or movements of this and/or movements of the unit, that is in the case of mobile units, in that the first reception area is considerably larger than the second reception area and in that the respective (mobile) units prepare themselves completely or partially before entry or re-entry into the first reception area.
 6. An arrangement according to any one of the preceding claims, characterized in that in the case where the mobile unit's current setting gives a sequence of time slots which coincides with the time slot sequence for the mobile unit scheduled in advance by the time slot system, the mobile unit is arranged to permit direct message transmission to or from other unit(s) in the arrangement when it enters into or is covered by the first reception area, and in that in the case where the tuning of the mobile unit gives a sequence of the mobile unit's time slots that differs from the sequence scheduled in advance in the arrangement, that is the mobile unit's sequence is out of phase with the scheduled sequence, the mobile unit exchanges information with the said devices and from these obtains correction or displacement of its time slot sequence so that it conforms with the scheduled sequence.
 7. An arrangement according to any one of the preceding claims, characterized in that the first reception area can be moved via the unit or units which are arranged to be fixed or mobile.
 8. An arrangement according to any one of the preceding claims, characterized in that the said reference time(s) emanate secondarily from master time generation which is arranged within a second reception area located inside the first reception area.
 9. An arrangement according to any one of the preceding claims, characterized in that a mobile unit that is located or ends up outside the first reception area (due to variation and/or movement of the first reception area and/or the mobile unit) obtains the reference time indication in the first reception area upon entry into the first reception area.
 10. An arrangement according to any one of the preceding claims, characterized in that updating and maintenance of accuracy of the reference time(s) of the first reception area are effected by one or more mobile units entering into or being covered by the second reception area at least temporarily for a predetermined minimum interval of time and thereby obtaining for other mobile units in the first reception area updated reference time(s) that can be transformed.
 11. An arrangement according to any one of the preceding claims, characterized in that the system works with or comprises a radio system of the Bluetooth type which works with symmetrical slots with predetermined frequency, that the system jumps between a number of frequencies, for example five frequencies, that respective mobile nodes incorporated in the system are pre-synchronized to the system by means of knowledge of an initial time (t), the algorithm for time slots for transmission and reception and for frequency jumping, and that as soon as it has entered into the fixed system the respective mobile node is synchronized only with the fixed network, which in turn is synchronized to the reference time system, that is the requirement that the mobile node is to be directly synchronized to the reference time system no longer applies.
 12. An arrangement according to any one of the preceding claims, characterized in that the mobile node is arranged to synchronize itself into the system as soon as it is able to synchronize itself to the time in the reference time system.
 13. An arrangement according to any one of the preceding claims, characterized in that respective mobile units first obtain or acquire the requisite protocol information before they enter into or are covered by the reception area in question.
 14. An arrangement according to any one of the preceding claims, characterized in that in the case where the reference time area is smaller than the network area, nodes concerned receive the requisite protocol information outside the reference time and network areas, that when it enters into or is covered by the network area the unit lacks the ability to synchronize itself to this, as it is not synchronized to the reference system, but the unit synchronizes itself to the reference time once it has entered into or is covered by the reference time area and when this has occurred the unit is arranged to calculated the correct frequencies and time slots and is able to connect itself to the network using other relevant protocol information and that when it is inside the network area the unit can thereafter leave the time reference area, as it is sufficient for the unit or units that are within the time reference area to be synchronized to the reference time.
 15. An arrangement according to any one of the preceding claims, characterized in that the units connected to the network that are outside the reference time area maintain the synchronization by using the time slots of the units synchronized to the reference time as secondary reference time indicators.
 16. An arrangement according to any one of the preceding claims, characterized in that at least any one unit in the network must enter the reference time area for re-synchronization before the time slots in the system fall outside acceptable tolerance levels.
 17. An arrangement according to any one of the preceding claims, characterized in that the system comprises or is based on advertising boards along one or more roads or sections of road along which vehicles or other mobile units move, that the advertising boards or the like are arranged with radio units, the coverage areas of which are not overlapping, meaning that they can have or utilize the same frequency arrangement and time slots and can work in a synchronous way and that the respective coverage areas have access to the reference time system, which preferably consists of the GPS system.
 18. An arrangement according to claim 17, characterized in that the vehicle or the like which moves along the road or section of road is in contact with and is synchronized to the reference system, that when the vehicle or the like passes the advertising boards, the vehicle or the like receives messages from the advertising boards.
 19. An arrangement according to claims 17 and 18, characterized in that the contact between the advertising boards and the vehicle or the like is two way and that information from the vehicle or the like is thus able to be transmitted to the advertising boards, that the coverage area for an advertising board consists of a predetermined distance along the road, which makes possible effective contact with the car or the like for a period of time, for example 1 second, if the vehicle is travelling at, for example, 100 km/hour.
 20. An arrangement according to any one of the preceding claims, characterized in that the coverage areas of the advertising boards overlap each other and that the advertising boards interact in a shared network, which means that the time slots are divided between them, whereby only one unit needs to be synchronized to the reference time system and other units can synchronize on the time slots in the network.
 21. An arrangement according to any one of the preceding claims, characterized in that the system is arranged with parallel road lanes, where each lane has two sets of traffic lights, one at the entrance and one at the exit, that a sensor is arranged at the entrance and the exit to each lane, which sensor detects the passing of the respective vehicle or the like, the respective lane is provided with a local wired network that is connected to a lane controller unit, to the traffic lights and to a number of radio units that are sequentially overlapped, which lane controller unit is in turn connected to a wired network, which is connected to a charging system via a road toll unit.
 22. An arrangement according to claim 21, characterized in that if there is no vehicle/car or the like in a lane, the entrance light shows green and the exit light shows red, that when a vehicle/car or the like passes the sensor the entrance light changes to red, after which the vehicle/car or the like passes the radio units that work in a synchronous way, that while the vehicle/car or the like passes the respective radio units, requisite information is exchanged for the purpose of charging for the road toll, and that thereafter the exit light changes to red and when the vehicle/car or the like has passed the exit sensor, the lane in question returns to its original status.
 23. An arrangement according to claim 21 or 22, characterized in that the radio units working in a synchronous way make possible the obtaining of a redundant connection to the passing vehicle/car or the like with good range in the longitudinal direction of the lane, but with a limited range in the transverse direction, where the propagation diagram in question can be improved or optimized by the use of directional antennas.
 24. An arrangement according to any one of the preceding claims, characterized in that the radio units are grouped in order to minimize crosstalk and message packet collisions between the lanes, and/or that the time slots are coordinated so that crosstalk or message packet collisions are eliminated.
 25. An arrangement according to any one of the preceding claims, characterized in that the respective local networks (64, 65, 66) operate with a time slot system in which the schedules are phase-displaced in frequency (in a known way) in each time slot and the channel frequency thus obtained in the respective time slots is allocated to a particular category, for example, customer or staff.
 26. An arrangement according to any one of the preceding claims, characterized in that a first channel frequency is allocated to the local network's customers and a second channel frequency is allocated to the local network's staff.
 27. An arrangement according to claim 26, characterized in that a first channel frequency (71′) is allocated to a first category of customer and a second channel frequency (72′) is allocated to a second category of customer.
 28. An arrangement according to any one of the preceding claims, characterized in that the channel frequency in accordance with the utilized signal protocol jumps at random and at the same time in accordance with algorithms incorporated in the protocol.
 29. An arrangement according to any one of the preceding claims, characterized in that the local networks (64, 65, 66) are arranged at petrol stations and that the mobile units are allocated or belong to the stations' customers.
 30. An arrangement according to any one of the preceding claims, characterized in that the scheduling is distributed and that separation of different categories, for example staff/customers, is carried out in time and/or frequency, and that the transmission in the radio apparatus (transmitter/receiver) concerned operates with directed transmissions in order that staff or customer apparatus in close proximity to other staff or customer apparatus will not be subject to interference.
 31. An arrangement according to to any one of the preceding claims, characterized in that the error-detection function utilizes detection of the signal strength and in certain cases (a multipath situation), also utilizes error-detection code in the signal protocol, changing of the antenna propagation and/or antenna direction.
 32. An arrangement according to any one of the preceding claims, characterized in that, prior to entering into a local network, the respective mobile unit refers to a basic signal protocol system with regard to utilized schedule, jump algorithms, protocol, transmissions, transmission direction, etc, by means of which basic system the mobile unit makes contact with the respective local network for changing to corresponding current parameters that apply in the local network.
 33. An arrangement according to any one of the preceding claims, characterized in that the local network is arranged to operate with a function for approving the entering mobile customers.
 34. An arrangement for establishing a common global time-keeping for a system, characterized in that each node incorporated in the system is allocated a local time that can either be the same as or related to a global time, that a schedule is drawn up for a number, preferably all, of the nodes in the system, which schedule has time slots referring to the global time for transmission and reception of messages, and that the time slots are distributed to each node that are allocated the messages that the node is intended to transmit or receive in such a way that receivers and destinations(s) for the majority of all messages can be determined only from knowledge of the system's schedule, the common global time keeping and the time slot in which the message is sent.
 35. An arrangement according to claim 34, characterized in that each receiver determines whether a message is destined for it by the time slot in which the message is sent being allocated to that receiver for the reception of messages.
 36. An arrangement according to claim 34 or 35, characterized in that messages that are received in time slots at other times than those covered by allocated time slots for reception are saved with information about the time slot or time of reception in order to re-send the message in the receiver's own transmission time slot, if so required.
 37. An arrangement according to claim 34, 35 or 36, characterized in that the signal strength of messages that have the correct bit content according to the protocol's error-detection mechanisms, but which are received in time slots other than those allocated to the node, are saved with information about the time slot or time of reception and this information is used in order to optimize the system.
 38. An arrangement according to any one of claims 34-37, characterized in that redundant information in the messages, for example sender, recipient, message identity, etc, is used to detect errors in the scheduling or implementation of the respective node's part of the schedule.
 39. An arrangement comprising units incorporated in the network system, characterized in that the units are able to be connected to the network system by means of a time base that is common to the network system, which time base lacks geographical relationship to the network's radio coverage, that the time base emanates from a time generation source that is completely independent in relation to the network, for example the GPS system, that parts of a utilized network protocol necessary for radio communication between the units, for example time slots and frequencies associated with these, are related to the reference time by means of algorithms, that is for a given time, which makes it possible for the relevant frequency and time slot to be calculated.
 40. An arrangement according to claim 39, characterized in that a virtual, geographically-independent network thereby exists, where all nodes that are intended to be incorporated are synchronized in advance to the network or the network system.
 41. An arrangement according to claim 39 or 40, characterized in that a sub-network that is limited by the radio range of the units incorporated in the sub-network is able to be established without, or with greatly simplified, hand-shaking procedures.
 42. An arrangement according to any one of claims 39-41, characterized in that the time messages in question are to be found on a previously selected frequency.
 43. An arrangement according to any one of claims 39-42, characterized in that the frequency is fixed and that the time message, in addition to comprising the actual time, also contains information or data that identifies the system and that a unit not connected to the system at the time in question is able to synchronize itself to the network on the messages that are due to be sent in order to maintain a global time in the system.
 44. An arrangement according to any one of claims 39-43, characterized in that the fixed network system in question is situated on a vehicle/car and that fixed and/or mobile nodes are able to be covered by the vehicle/car's network.
 45. An arrangement with a number of units which can communicate with each other via a wireless connection system for the transmission of messages with control information data (commands) and/or process data where the connection system works with a first reception area and a time slot system established in this by some means, in which time slot system the units have access to the relevant transmission media in allocated and sequential time intervals (time slots), in which intervals the units are activated for their transmissions or receptions by means of time information executed in the time slot system, referring to one or more reference times utilized in the time slot system, characterized in that the said reference time(s) emanate secondarily from master time generation that is arranged within a second reception area located inside the first reception area, that a unit that is located or ends up outside the first reception area (due to variation and/or movement of the first reception area and/or movement of the unit), obtains reference time indication when the unit is covered by the first reception area or enters into the first reception area, and that updating and maintaining of the accuracy of the first area's reference time(s) can be effected by one or more mobile units entering, being covered by or being located in the second reception area at least temporarily for a predetermined minimum interval of time, and obtaining for other mobile units in the first reception area updated reference time(s) that can be transformed.
 46. A method of connecting units to a network system, characterized by: a) obtaining a given protocol for the system, b) synchronization of the system's global time and c) in the case where allocated time slots are obtained in accordance with a), transmission/reception according to the protocol commences directly, or in the case where allocated time slots are not obtained, these are obtained according to rules in accordance with a) and transmission/reception according to the protocol can thereafter commence. 